Soluble transferrin receptor in urine, a new biomarker for IgA nephropathy and Henoch-Schonlein purpura nephritis

Objectives: IgA nephropathy (IgAN) and Henoch-Schonlein purpura nephritis (HSPN) might represent different ends of a continuous spectrum of glomerular disease. In both conditions, upregulated soluble transferrin receptor (sTfR) might be excreted in urine, which could be a potential biomarker to monitor disease activity and therapeutic response. Methods: In this pilot study, 132 Caucasian patients consulting the Nephrology Department at the Ghent University Hospital because of a glomerulopathy and 50 normal controls were included. Urinary sTfR concentrations were determined in concentrated urine using a newly developed latex-enhanced immunonephelometric assay. Results: Median urinary sTfR concentration was higher in patients with a primary glomerulopathy than in healthy subjects (p<0.0001). More importantly, absolute median levels of urinary sTfR were markedly higher in patients with active IgAN or HSPN [10 mu g/L, 95% confidence interval (CI): 6-18 mu g/L] in comparison with those with other morphological types of glomerulopathy (2 mu g/L, 95%CI: 1-4 mu g/L) (p<0.0001). A statistically significant difference in urinary sTfR concentration was observed between patients with active IgAN or HSPN and patients who had achieved partial or complete remission (p<0.0001). Multiple regression analysis with urinary sTfR as dependent variable revealed that proteinuria was the main predictor of urinary sTfR concentration (r(2)=0.52, p<0.001). Conclusion: Determination of sTfR in urine is a new and sensitive method for a potential biomarker of IgAN and HSPN. (C) 2013 The Canadian Society of Clinical Chemists. Published by Elsevier Inc. All rights reserved.